Thermal shroud



Jan. 31, 1967 J. B. MERRILL 3,301,319

THERMAL SHROUD Filed March 23, 1965 2 Sheets-Sheet 1 E A? I J 1 a a 15295:

Josqvk/B.Me3 a1iZZ, by 3,11% 7W United States Patent Gill-ice 3,361,319 Patented Jan. 31, 1967 3,301,319 THERMAL SHROUD Joseph B. Merrill, Cohasset, Mass., assignor to High Vacuum Equipment Corporation, Hingham, Mass., a corporation of Massachusetts Filed Mar. 23, 1965, Ser. No. 453,859 4 Claims. (Cl. 165-133) The invention relates in general to heat transfer devices, and pertains more particularly to devices referred to as thermal shrouds for use in vacuum chambers to absorb heat and produce conditions of extreme cold, or, alternatively, to transmit heat to an object mounted in the chamber. This application is a continuation in part of my previous application Serial No. 190,686, filed April 27, 1962, now abandoned.

Under high vacuum conditions heat transfer between bodies spaced from one another takes place by radiation only, because there is no atmosphere to transmit heat by conduction or convection. Vacuum chambers are frequently used to simulate conditions of outer space for the purpose of testing articles and materials for use in space. It is customary to surround the work area, in which the objects are to be tested, by an enclosure or shroud having a highly emissive and absorbent inner surface. The shroud may be cooled by cryogenic fluid to carry away heat radiated by objects under test, or heated to act as a radiator, to test the object under controlled low or high temperature conditions in vacuum.

Althought the improvement of radiant heat transfer between a shroud and an object spaced from it is particularly applicable to vacuum conditions, the same problem also exists to a considerable degree in gaseous atmospheres under conditions where there is very little circulation of the atmosphere. Under such conditions, heat transfer .by convection is low, and as gases are poor condoctors, most of the heat transfer must take place by radiation.

The principal object of this invention is to provide a shroud material which has very high heat absorption and emission properties over the entire range of visible and infra red bands of the electro-magnetic energy spectrum so as to produce efficient and rapid heating and cooling under high vacuum conditions or in gaseous atmospheres with low circulation. Another object is to provide a shroud construction which may be easily varied in shape or size by using different arrangements of a basic structural element.

The shroud assembly here disclosed is made up of a number of like panels having interlocking beads and grooves along their edges, so that any number of panels may be assembled together to vary the size of the assembly. The panels are made of material such as extruded aluminum and are polished on the outside to reduce radiant heat transfer to a minimum. On the inside, the panels have a number of inwardly projecting ribs of steep isosceles triangular configuration, spaced apart by troughs. The ribs have a number of furrows along their sides providing multiple reflecting surfaces which tend to reflect any radiation which strikes the sides of the ribs, and is not immediately absorbed, back toward the troughs. The inner surfaces of the panels are also treated to provide for maximum absorption so that practically all heat or light radiation coming from an object in the work area is absorbed by the panels. The panels have conduits through which cold liquid is circulated when the shroud is used :as a heat sink, and hot liquid is circulated when the shroud is used as a radiator. Other objects, advantages, and novel features will be apparent from the following detailed description.

In the drawing illustrating the invention:

FIG. 1 is a side elevation of a thermal shroud constructed according to the invention;

FIG. 2 is an enlarged cross-section taken along line 2-2 of FIG. 1;

dFIG. 3 is an enlarged cross-section of one of the panels; an

FIG. 4 is a fragmentary cross-section, further enlarged, of a panel in the region of a pair of ribs.

A typical shroud, as shown in FIGS. 1 and 2, is a cylinder made up of a number of panels 10, having their conduits 11 connected to a header 12 and a return pipe 13. A table 14, on which the object to be treated or tested may be placed, is mounted within the shroud. The header 12 and return pipe 13 are connected in a suitable circulating system (not shown) for circulating liquid, for example brine, through conduits 11. The liquid may be heated or cooled to the desired temperature. When in operation the shroud assembly is mounted in a vacuum chamber which is evacuated to the degree required for the particular test or other operation, or may contain an inert gas. The panels are made of a suitable heat conductive material such as aluminum, -and may conveniently be manufactured "by extruding long sections and cutting them to the length required for the particular installation.

Each panel 10 has a bead 15 along one longitudinal edge, and an undercut groove 16, in which the bead of the adjoining panel is received, along its opposite edge. The panels are assembled together by sliding the bead of one longitudinally into the groove of the next. As best shown in FIG. 3, the head is connected to the panel :by a reduced neck 15a, and the groove has an entrance 1 6a slightly wider than the neck. There is suflicient clearance between the groove and the bead of the adjoining panel (shown in broken line) to permit hinging action so that the relative angles of the panels can be adjusted to make shroud assemblies of different circumferences by varying the number of panels used.

The panel has a body portion 10a which may be slightly curved, or may be straight as a large enough number of panels are ordinarily used in a shroud assembly so that the overall shape approximates a cylinder even when the shroud is composed of straight panels.

The outer surface 10b of the panels is smooth and highly polished to minimize heat radiation from the shroud toward the outside. Extending inward from the body portion 10a are a number of ribs 17 separated by troughs 18. The ribs are of steep isosceles triangular configuration and have a number of furrows 19 along their oblique sides. The under surfaces 19a of the furrows are substantially parallel to the body portion. The troughs 18 have curved bases 18a, giving the troughs, as a whole, a generally parabolic configuration. The ends of the ribs are brought practically to a point, but may be formed with a small radius to facilitate fabrication. All the surfaces of the ribs and troughs are finished dull or blackened for maximum absorption.

The action of the panels, when subject to radiation from the work area, is illustrated in FIG. 4. When a ray strikes any of the inner surfaces, a considerable portion of its energy is absorbed, but a certain percentage is reflected. However, only rays impinging directly on the negligible areas represented by the center lines of the ends of the ribs and of bases 18a, such as rays A and B, are reflected back toward the work area. Rays impinging on the panel at other points, such as rays C and D, are reflected on to the multiple surfaces provided by the furrows 19, usually several times as indicated by the path of ray C. As a large percentage of the energy is absorbed each time the reflected ray strikes one of these surfaces, practically all of its energy is absorbed before the ray can be deflected in a direction to return toward the work area. The panel is made of a good heat conductor, so that the absorbed heat is quickly transmitted through body portion a to the liquid in conduits 11. The panel is very effective in absorbing and carrying off heat radiated from the Work area and thus lowering the temperature of an object placed within that area.

When the panel is used as a radiator, heat from the liquid in conduit 11 is transmitted to ribs 17. The multiple surfaces of furrows 19 provide a large surface area for radiation, and the parabolic shape of the troughs results in focussing of the radiated heat toward the center of the Work area. The panel is thus very effective in raising the temperature of an object Within that area.

Shrouds of the construction there disclosed are relatively simple and inexpensive to manufacture. The panel material can be formed as a continuous extrusion and cut into panels of the desired length. No tools, fastenings, or special machinery are required for assembling the panels together. The same basic panels may be used to construct shoruds of various shapes, for example, a

straight wall, or an oval, as Well as a cylinder, and the size of the assembly may be varied simply by varying the number of panels used.

The shroud panels may be assembled with the ribs running vertically, horizontally, or obliquely. In a high vacuum the disposition of the ribs is immaterial from the standpoint of heat transfer. In a gaseous atmosphere, vertical disposition of the ribs is generally preferable as it assists the flow of whatever convection currents may be present. In any case, the panels provide effective transfer of radiant heat to or from an object spaced from the shroud on the ribbed side.

hat is claimed is:

1. A heat absorbent and radiant panel for use in making a thermal shroud embodying a plurality of said panels 4 wherein each panel comprises a :body portion having an outer side and an inner side and a number of spaced parallel inwardly extending ribs on said inner side, each of said ribs being of generally triangular cross-section and having side walls diverging toward said body portion,-

said body portion having curved surfaces on said inner side between adjacent ribs said surfaces defining, with the side Walls of the adjacent ribs generally parabolic troughs parallel to the ribs, said side walls being provided with longitudinal furrows, each of said furrows having an inner surface disposed at such an angle as to deflect radiation impinging thereon toward the confronting adjacent side wall and an under surface facing toward said parabolic trough.

2. A panel as described in claim 1, having a fluid conduit in said body portion.

3. A panel as described in claim 1, said ribs having substantially pointed inner edges.

4. A panel as described in claim 1, said body portion having a highly reflective outer surface.

References Cited by the Examiner UNITED STATES PATENTS 2,077,927 4/1937 Glenn -169 X 2,372,155 3/1945 Bosch 165133 X 3,081,824 3/1963 Macall 165185 3,149,666 9/1964 Coe. 3,163,207 12/ 1964 Schultz 165-68 FOREIGN PATENTS 304,779 3/ 1930 Great Britain.

82,550 10/ 1953 Norway.

ROBERT A. OLEARY, Primary Examiner.

T. W. STREULE, ]R., Assistant Examiner. 

1. A HEAT ABSORBENT AND RADIANT PANEL FOR USE IN MAKING A THERMAL SHROUD EMBODYING A PLURALITY OF SAID PANELS WHEREIN EACH PANEL COMPRISES A BODY PORTION HAVING AN OUTER SIDE AND AN INNER SIDE AND A NUMBER OF SPACED PARALLEL INWARDLY EXTENDING RIBS ON SAID INNER SIDE, EACH OF SAID RIBS BEING OF GENERALLY TRIANGULAR CROSS-SECTION AND HAVING SIDE WALLS DIVERGING TOWARD SAID BODY PORTION, SAID BODY PORTION HAVING CURVED SURFACES ON SAID INNER SIDE BETWEEN ADJACENT RIBS SAID SURFACES DEFINING, WITH THE SIDE WALLS OF THE ADJACENT RIBS GENERALLY PARABOLIC TROUGHS PARALLEL TO THE RIBS, SAID SIDE WALLS BEING PROVIDED WITH LONGITUDINAL FURROWS, EACH OF SAID FURROWS HAVING AN INNER SURFACE DISPOSED AT SUCH AN ANGLE AS TO DEFLECT RADIATION IMPINGING THEREON TOWARD THE CONFRONTING ADJACENT SIDE WALL AND AN UNDER SURFACE FACING TOWARD SAID PARABOLIC TROUGH. 